ABSTRACT
Athletic mental energy is a newly emerging research topic in sport science. However, whether it can predict objective performance in competition remains unexplored. Thus, the purpose of this study was to examine the predictability of mental energy on volleyball competition performance. We recruited 81 male volleyball players (Mage = 21.11 years ± SD = 1.81) who participated in the last 16 remaining teams in a college volleyball tournament. We assessed participants' mental energy the night before the competition and collected their competition performance over the next 3 days. We used six indices of the Volleyball Information System (VIS) developed by the International Volleyball Federation (FIVB) to examine its associations with mental energy. All six factors of mental energy -motivation, tirelessness, calm, vigor, confidence, and concentration correlated with volleyball competition performance. Further, a hierarchical regression found mental energy predicted volleyball receivers' performance (R2 = .23). The findings advance our knowledge of mental energy and objective performance in competition. We suggest that future studies may examine the effects of mental energy on different sports with different performance indices.
Subject(s)
Volleyball , Humans , Male , UniversitiesABSTRACT
In this study, the transfer process of extremely light and small-sized particles along a defined direction without flipping them over on the transportation surface is evaluated by using a traveling wave. For this, the use of a liquid, as the contact layer injected onto the top surface of a piezoelectric traveling-wave device, is proposed to transmit the wave into the particles. As a preload is unlikely to be assigned here, the adhesion force between the lightweight particle and the liquid is expected to dominate the delivery effect. A short-beam linear motor is chosen as an example of a piezoelectric device that can generate a traveling wave in association with several selected liquids such as water, saline water, oil, and glycerol. The influence on the traveling-wave amplitude transmitted to liquids with different viscosities and heights is studied by an analytical approach and the finite-element simulation. The surface energy theory is used to determine the adhesion force between the liquid and the lightweight particle. An experiment is conducted to measure the speed of particles with variable sizes that are transported by the liquid wave. The analytical and experimental results are in good agreement, verifying the influence of the above concerned factors on the particle transfer speed.
Subject(s)
Computer SimulationABSTRACT
A straight short-beam linear piezoelectric motor constructed with two sets of ceramic actuators separated with the 1/4 wavelength interval is designed in this article. The piezoelectric ceramic actuators are fabricated in the whole body, which is driven by a two-phase circuit with the same amplitude but a phase difference of π /4. Traveling wave (TW) is formed by superimposing standing waves generated by each set of ceramic actuators. At the ends of the short beam, a wave-reduction mechanism with larger cross-sectional area is designed so that wave reflection is effectively diminished to preserve the TW. The currently developed short-beam linear piezoelectric motor is estimated, which can produce an ideal output speed of 169 mm/s while applying voltage of Vpp = 300 V at 45.49 kHz. Instead of operating as a stator to drive a carriage for example, the short-beam linear piezoelectric motor is implemented on a guide slider, and therefore, a linear piezoelectric motor stage is built. While driving the linear stage employed with a preload 300 GW and a friction coefficient of about 0.15, the propulsion force is measured about 4.8 N, the speed is about 56 mm/s, and the position resolution can achieve in the submicrometer scale.
